Mississippi Sandhill Crane Recovery

Crane Colts

The Mississippi Sandhill Crane National Wildlife Refuge was created to maintain and restore some of the last large acres of wet pine savanna. The savanna is important to crane roosting, nesting and foraging. Cranes can also be seen foraging on private lands where the grass is short and provides for tubers, grasshoppers and other delectables.

At the refuge, a tremendous amount of work is done to restore the natural ecosystems used by the cranes and other wildlife. In addition to restoring the savanna and creating a home for the cranes, biologists spend the year tracking and monitoring the cranes.

Tracking and Monitoring

 

Through tracking and monitoring the cranes, information is obtained on each bird and is put in a refuge data base which will provide clues to habitat use, nesting, survival rates, cause of mortality, and many other aspects of local crane life.


Protecting the cranes requires partnerships with other agencies and private landowners. One of the first things refuge biologists must know is where and how many cranes there are - then it's a matter of monitoring and protecting them as needed.

Official estimates of crane numbers are figured in January based on information gathered at several official crane counts, including the Fall Crane Count.

Year round monitoring is conducted with biologists spending the early mornings in blinds hoping to catch a glimpse of the birds and tracking the birds using radio telemetry.

Many birds on the refuge are outfitted with a radio transmitter. Using antenna equipment, biologists go out into the refuge and in the community to track the signal produced by the transmitter. Each radio has signal on a different frequency.

Using telemetry - taking several points where the signal is picked up - biologists are able to find, identify and monitor the cranes. Radio transmitters have small batteries in them with an estimated life of 2 years. Not all cranes get radio transmitters, but almost all are banded with brightly colored leg bands. These band combinations are unique to each bird and allow the biologists to identify the birds from a distance.

Each of these methods helps the refuge to identify the birds, document their bonds and behaviors and conduct research on them that will be useful for their recovery and for recovery of other endangered cranes.

During the winter, biologists attempt to trap the cranes to outfit them with new transmitters, band young birds and replace bands where they have fallen off of older birds. 


In the spring, biologists search for cranes and monitor their nests. Egg viability is then tested using a 'floating egg test'. For this test, an egg is placed in a container of water. If the egg is viable, it will exhibit small movements while floating in the water.

Other tests identify how far along the nest is into the incubation period. Biologists can watch for chicks and record how many cranes are hatched.

It's important to locate nests each year for crane recovery data, but also to plan the fire management around units and areas where the cranes are nesting.

Cranes are often 3-4 years old or older before they find a mate and form a pair bond. After that, pairs can nest for 2-3 years before they lay viable eggs. They generally lay 1-2 eggs, but it is rare for more than one of the offspring to be reared to fledging. 

Reared in Captivity

 

Natural recruitment is one of the limiting factors to crane population growth each year. Predators make life difficult for parents guarding the nest and young cranes, called colts, trying to survive. Crane parents have been observed successfully protecting their eggs from owls and other predators.

If predators such as bobcats, armadillos, or raccoons find the nests and destroy the eggs, pairs will often attempt to nest again. Crane parents will raise the young colt until it is about 10 months old and nearly full grown.

To help grow the crane population, the refuge uses a system of captive rearing. Each year, 10-15 young birds are released on the refuge.

Beginning in 1965, "extra" eggs, the second viable egg from a two-egg nest, were occasionally removed from the local nests and taken to the U.S.G.S. Patuxent Wildlife Research Center to become part of a captive flock. This flock was useful as a genetic reservoir and for physiological and behavioral research that would be difficult with wild birds.

By 1980, there were enough captive breeding pairs to produce juveniles for release.

While in captivity it is very important that the colts do not imprint on humans. To avoid this, their human handlers wearing a crane costume which obscures the human form and allows the handler to manipulate the colt's environment using a crane hand puppet. Using this puppet to demonstrate, young cranes learn life skills. They imprint to the puppet and the remainder of the costume is a simple "grey blob" to them.

After the cranes are fully grown, they are captured, banded and brought to the refuge. They are released into large pens with a braille on their wings to keep them from flying away while they acclimate to their new home and surroundings.

Continuing with the captive rearing system, anytime biologists take food to the cranes, they wear the crane costume. After a month, the cranes are re-captured, the brailles are taken off of their wings, and they are able to leave the pens and join the rest of the population in the wild.

Since 1981, captive reared cranes have been released annually on the refuge. This program is the largest crane release program in the world and has been so successful that 90 percent of the free-flying cranes seen today are captive-reared.

Mississippi Sandhill Crane Species Profile 

Mississippi Sandhill Crane Biology